Fix admin user can create top level group UI

What does this MR do and why?

This MR changes the test for whether a user can create a group from User#can_create_group to User#can_create_group?.

The can_create_group is a property in the users table and is initialized to the application settings.

The check User#can_create_group has been unchanged since added in 2013 74a62138. At that point, the User#can_create_group? method which is a permission check existed, so it's possible that the view file intentionally was not using #can_create_group?.

But it seems like the admin is likely to want to know whether the user has permission to create groups.

For example, a placeholder user, who has no permissions previously could be listed as having create group ability. After this change, they are listed as not having create group ability.

https://gitlab.com/gitlab-org/manage/import-and-integrate/discussions/-/issues/112#note_2081598947

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Screenshots or screen recordings

A placeholder user, who has no permissions previously was listed as having create group ability. After this change, they are listed as not having create group ability.

Before	After

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